Conventionally, in optical communications using an optical transmission member such as an optical fiber or an optical waveguide, an optical module including a light emitting element such as a surface-emitting laser (for example, a vertical cavity surface emitting laser (VCSEL)) has been used. The optical module includes one or more photoelectric conversion elements (light emitting elements or light receiving elements), and a light coupling element for transmission and reception (hereinafter also referred to as an “optical receptacle”).
In an optical module for optical communications, the quantity of light emitted from an optical receptacle for transmission is required to be attenuated for ensuring safety, and thus an optical filter for attenuating the quantity of the light emitted from the optical receptacle for transmission may be used (see, for example, PTL 1).
FIG. 1 is a cross-sectional view of optical receptacle 1 described in PTL 1. Optical receptacle 1 described in PTL 1 includes optical receptacle body 2 and optical filter 3 (for example, light-attenuating filter). As illustrated in FIG. 1, optical receptacle body 2 includes lens surfaces 4 arranged in a line at equal intervals on the bottom surface of optical receptacle body 2, and optical surface 5 disposed opposite lens surfaces 4. Optical filter 3 is disposed on a part of optical surface 5. Optical receptacle 1 described in PTL 1 is used with photoelectric conversion device which has a plurality of light emitting elements and light receiving elements and which is disposed on the lens surface 4 side, and with a plurality of optical transmission members which are disposed on the optical surface 5 side. In optical receptacle 1 described in PTL 1, optical filter 3 is disposed on the optical path of light emitted from the light emitting elements and incident on the optical transmission members, thereby attenuating the quantity of the light emitted from optical receptacle 1 on the transmission side.